The present invention relates to the control of fouling by protein-containing fluids in equipment used in the wet milling of corn. The wet milling processing of shelled corn is employed to obtain staple products such as corn oil, dextrose, corn syrup, high fructose corn syrup, dextrins, dry starches and feeds. The principle steps in the wet milling of corn include steeping, milling, recovering and processing. During the steeping operation, corn kernels are softened by soaking in a hot, dilute solution of sulfurous acid (i.e., water/sulfur dioxide). The softened kernels are then passed through grinding mills and separators where the germ is removed and the starch and gluten are separated from the coarser hull and fibers. The starch is then separated from the gluten which is added to the fibrous material and processed into a high protein animal feed. The starch is recovered as dry starch or further processed into dextrose and fructose. The sulfurous acid steepwater initially used to soften the corn contains solubles which are recovered for use in feeds. The steepwater solids are recovered by evaporation and drying. The solids recovered from evaporating and drying the steepwater are used as additives to live stock feeds to enhance their nutritional value.
The deposition of organic, proteinaceous materials in the steepwater evaporators limits throughput and is a bottle-neck in the wet milling corn process. To cope with such organic deposition fouling, such evaporators are typically boiled out with an acid and/or caustic solution. Such boil-out procedures result in undesirable downtime for the equipment. The present invention is directed to a process for controlling deposition in such evaporators so as to minimize the requirement for such boil-out procedures.
The use of surfactants to control particle adhesion and cohesion of proteinaceous materials such as wheat gluten is known. U.S. Pat. No. 3,362,829 discloses a process for coating powdered vital wheat gluten with a nonionic hydrophilic lipid selected from the class consisting of monoglycerides, salts of lactylic esters of fatty acids, polyoxyethylene stearate and stearyl monoglyceridyl citrate. The coating of the powdered wheat gluten with such nonionic hydrophilic lipids is disclosed as controlling wetting of the vital wheat gluten thereby controlling cohesion of the gluten upon hydrogenation. The use of polyoxyethylene sorbitan monostearate in combination with the hydrophilic lipids is also disclosed. The surface active agent, i.e., polyoxyethylene sorbitan monostearate is included as an aid for the initial dispersion of the vital wheat gluten and has no inhibiting effect on coalescence of the vital wheat gluten. The process of hydrating vital wheat gluten described in U.S. Pat. No. 3,362,829 is typically carried out at neutral pH and relatively low temperatures so as to not substantially denature the gluten.
U.S. Pat. No. 3,880,824 discloses a gluten/lipid complex and process for preparing a gluten/lipid complex in which vital wheat gluten complexes with lipids are prepared which are resistant to particle cohesion. The finely divided vital wheat gluten is reacted with ionic and nonionic fatty substances selected from the group consisting of fatty acid chlorides, fatty monoglycerides, lactylic esters of fatty acids, phospholipids and sorbitan fatty acid esters in the presence of a mild base catalyst. The phospholipids and lactylic esters of fatty acids yield comparable complexes in an acidic environment.
U.S. Pat. No. 1,918,812 discloses a treatment for steepwater from a wet corn milling operation which minimizes scale in the steepwater evaporators. The process comprises "incubating" the steepwater to allow natural organisms and/or enzymes to convert the scale forming substances into non-scale forming substances. A carbohydrate may be added to the steepwater which may also be agitated or aerated to hasten the desired effect of the organisms and/or enzymes.
An additive to control scale formation in evaporators used in the concentration of cane and beet sugar is disclosed in U.S. Pat. No. 3,483,033. The additive is a composition containing a hydrolyzed polyacrylamide and a protective colloid such as sodium alginate or carboxymethylcellulose and preferably one or more of (1) EDTA or disodium methylene diamine tetraacetic dihydrate, (2) a gluconate, and (3) a polyphosphate. The composition is added to sugar juice after clarification and before the evaporators to control scale deposition in the evaporators.